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1.
We report the effects of Ca2+ binding on the backbone relaxation rates and chemical shifts of the AD and BD splice variants of the second Ca2+‐binding domain (CBD2) of the sodium–calcium exchanger. Analysis of the Ca2+‐induced chemical shifts perturbations yields similar KD values of 16–24 μM for the two CBD2‐AD Ca2+‐binding sites, and significant effects are observed up to 20 Å away. To quantify the Ca2+‐induced chemical shift changes, we performed a comparative analysis of eight Ca2+‐binding proteins that revealed large differences between different protein folds. The CBD2 15N relaxation data show the CBD2‐AD Ca2+ coordinating loops to be more rigid in the Ca2+‐bound state as well as to affect the FG‐loop located at the opposite site of the domain. The equivalent loops of the CBD2‐BD splice variant do not bind Ca2+ and are much more dynamic relative to both the Ca2+‐bound and apo forms of CBD2‐AD. A more structured FG‐loop in CBD2‐BD is suggested by increased S2 order parameter values relative to both forms of CBD2‐AD. The chemical shift and relaxation data together indicate that, in spite of the small structural changes, the Ca2+‐binding event is felt throughout the molecule. The data suggest that the FG‐loop plays an important role in connecting the Ca2+‐binding event with the other cytosolic domains of the NCX, in line with in vivo and in vitro biochemical data as well as modeling results that connect the CBD2 FG‐loop with the first Ca2+‐binding domain of NCX. Proteins 2010. © 2010 Wiley‐Liss, Inc. 相似文献
2.
Ca2+ is a highly versatile second messenger that plays a key role in the regulation of numerous cell processes. One‐way cells ensure the specificity and reliability of Ca2+ signals is by organizing them spatially in the form of waves that propagate throughout the cell or within a specific subcellular region. In non‐excitable cells, the inositol 1,4,5‐trisphosphate receptor (IP3R) is responsible for the release of Ca2+ from the endoplasmic reticulum. The spatial aspect of the Ca2+ signal depends on the organization of various elements of the Ca2+ signaling toolkit and varies from tissue to tissue. Ca2+ is implicated in many of endothelium functions that thus depend on the versatility of Ca2+ signaling. In the present study, we showed that the disruption of caveolae microdomains in bovine aortic endothelial cells (BAEC) with methyl‐ß‐cyclodextrin was not sufficient to disorganize the propagation of Ca2+ waves when the cells were stimulated with ATP or bradykinin. However, disorganizing microfilaments with latrunculin B and microtubules with colchicine both prevented the formation of Ca2+ waves. These results suggest that the organization of the Ca2+ waves mediated by IP3R channels does not depend on the integrity of caveolae in BAEC, but that microtubule and microfilament cytoskeleton assembly is crucial. J. Cell. Biochem. 106: 344–352, 2009. © 2008 Wiley‐Liss, Inc. 相似文献
3.
Le Chang Eric J. Dykes Jianhua Li Silvia N.J. Moreno Miryam Andrea Hortua Triana 《The Journal of eukaryotic microbiology》2019,66(2):343-353
The universal role of calcium (Ca2+) as a second messenger in cells depends on a large number of Ca2+‐binding proteins (CBP), which are able to bind Ca2+ through specific domains. Many CBPs share a type of Ca2+‐binding domain known as the EF‐hand. The EF‐hand motif has been well studied and consists of a helix‐loop‐helix structural domain with specific amino acids in the loop region that interact with Ca2+. In Toxoplasma gondii a large number of genes (approximately 68) are predicted to have at least one EF‐hand motif. The majority of these genes have not been characterized. We report the characterization of two EF‐hand motif‐containing proteins, TgGT1_216620 and TgGT1_280480, which localize to the plasma membrane and to the rhoptry bulb, respectively. Genetic disruption of these genes by CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR‐associated protein 9) resulted in mutant parasite clones (Δtg216620 and Δtg280480) that grew at a slower rate than control cells. Ca2+ measurements showed that Δtg216620 cells did not respond to extracellular Ca2+ as the parental controls while Δtg280480 cells appeared to respond as the parental cells. Our hypothesis is that TgGT1_216620 is important for Ca2+ influx while TgGT1_280480 may be playing a different role in the rhoptries. 相似文献
4.
5.
Jing Hui Xue Hiroko Takahashi Masayoshi Yamaguchi 《Journal of cellular biochemistry》2001,80(2):285-292
The effect of regucalcin, which is a regulatory protein of Ca2+ signaling, on Ca2+‐ATPase activity in isolated rat renal cortex mitochondria was investigated. The presence of regucalcin (50, 100, and 250 nM) in the enzyme reaction mixture led to a significant increase in Ca2+‐ATPase activity. Regucalcin significantly stimulated ATP‐dependent 45Ca2+ uptake by the mitochondria. Ruthenium red (10−6 M) or lanthunum chloride (10−6 M), an inhibitor of mitochondrial Ca2+ uptake, markedly inhibited regucalcin (100 nM)‐increased mitochondrial Ca2+‐ATPase activity and 45Ca2+ uptake. The effect of regucalcin (100 nM) in elevating Ca2+‐ATPase activity was completely prevented by the presence of digitonin (10−2%), a solubilizing reagent of membranous lipids, vanadate, an inhibitor of phosphorylation of ATPase, or dithiothreitol (50 mM), a protecting reagent of the sulfhydryl (SH) group of the enzyme. The activating effect of regucalcin (100 nM) on Ca2+‐ATPase activity was not further enhanced by calmodulin (0.30 μM) or dibutyryl cyclic AMP (10−4 M), which could increase Ca2+‐ATPase activity. Trifluoperazine (TFP; 50 μM), an antagonist of calmodulin, significantly decreased Ca2+‐ATPase activity. The activating effect of regucalcin on the enzyme was also seen in the presence of TFP, indicating that regucalcin's effect is not involved in mitochondrial calmodulin. The present study demonstrates that regucalcin can stimulate Ca2+‐pump activity in rat renal cortex mitochondria, and that the protein may act on an active site (SH group) related to phosphorylation of mitochondrial Ca2+‐ATPase. J. Cell. Biochem. 80:285–292, 2000. © 2000 Wiley‐Liss, Inc. 相似文献
6.
Daeshik Cho Sun A. Kim Yoshiyuki Murata Sangmee Lee Seul-Ki Jae Hong Gil Nam June M. Kwak 《The Plant journal : for cell and molecular biology》2009,58(3):437-449
Cytosolic Ca2+ ([Ca2+]cyt) mediates diverse cellular responses in both animal and plant cells in response to various stimuli. Calcium oscillation amplitude and frequency control gene expression. In stomatal guard cells, [Ca2+]cyt has been shown to regulate stomatal movements, and a defined window of Ca2+ oscillation kinetic parameters encodes necessary information for long‐term stomatal movements. However, it remains unknown how the encrypted information in the cytosolic Ca2+ signature is decoded to maintain stomatal closure. Here we report that the Arabidopsis glutamate receptor homolog AtGLR3.1 is preferentially expressed in guard cells compared to mesophyll cells. Furthermore, over‐expression of AtGLR3.1 using a viral promoter resulted in impaired external Ca2+‐induced stomatal closure. Cytosolic Ca2+ activation of S‐type anion channels, which play a central role in Ca2+‐reactive stomatal closure, was normal in the AtGLR3.1 over‐expressing plants. Interestingly, AtGLR3.1 over‐expression did not affect Ca2+‐induced Ca2+ oscillation kinetics, but resulted in a failure to maintain long‐term ‘Ca2+‐programmed’ stomatal closure when Ca2+ oscillations containing information for maintaining stomatal closure were imposed. By contrast, prompt short‐term Ca2+‐reactive closure was not affected in AtGLR3.1 over‐expressing plants. In wild‐type plants, the translational inhibitor cyclohexamide partially inhibited Ca2+‐programmed stomatal closure induced by experimentally imposed Ca2+ oscillations without affecting short‐term Ca2+‐reactive closure, mimicking the guard cell behavior of the AtGLR3.1 over‐expressing plants. Our results suggest that over‐expression of AtGLR3.1 impairs Ca2+ oscillation‐regulated stomatal movements, and that de novo protein synthesis contributes to the maintenance of long‐term Ca2+‐programmed stomatal closure. 相似文献
7.
Jyothilakshmi Vadassery Stefanie Ranf Corinna Drzewiecki Axel Mithöfer Christian Mazars Dierk Scheel Justin Lee Ralf Oelmüller 《The Plant journal : for cell and molecular biology》2009,59(2):193-206
Calcium (Ca2+), as a second messenger, is crucial for signal transduction processes during many biotic interactions. We demonstrate that cellular [Ca2+] elevations are early events in the interaction between the plant growth‐promoting fungus Piriformospora indica and Arabidopsis thaliana. A cell wall extract (CWE) from the fungus promotes the growth of wild‐type seedlings but not of seedlings from P. indica‐insensitive mutants. The extract and the fungus also induce a similar set of genes in Arabidopsis roots, among them genes with Ca2+ signalling‐related functions. The CWE induces a transient cytosolic Ca2+ ([Ca2+]cyt) elevation in the roots of Arabidopsis and tobacco (Nicotiana tabacum) plants, as well as in BY‐2 suspension cultures expressing the Ca2+ bioluminescent indicator aequorin. Nuclear Ca2+ transients were also observed in tobacco BY‐2 cells. The Ca2+ response was more pronounced in roots than in shoots and involved Ca2+ uptake from the extracellular space as revealed by inhibitor studies. Inhibition of the Ca2+ response by staurosporine and the refractory nature of the Ca2+ elevation suggest that a receptor may be involved. The CWE does not stimulate H2O2 production and the activation of defence gene expression, although it led to phosphorylation of mitogen‐activated protein kinases (MAPKs) in a Ca2+‐dependent manner. The involvement of MAPK6 in the mutualistic interaction was shown for an mpk6 line, which did not respond to P. indica. Thus, Ca2+ is likely to be an early signalling component in the mutualistic interaction between P. indica and Arabidopsis or tobacco. 相似文献
8.
Juyou Wu Zhonglin Shang Jun Wu Xueting Jiang Panagiotis N. Moschou Wending Sun Kalliopi A. Roubelakis‐Angelakis Shaoling Zhang 《The Plant journal : for cell and molecular biology》2010,63(6):1042-1053
Spermidine (Spd) has been correlated with various physiological and developmental processes in plants, including pollen tube growth. In this work, we show that Spd induces an increase in the cytosolic Ca2+ concentration that accompanies pollen tube growth. Using the whole‐cell patch clamp and outside‐out single‐channel patch clamp configurations, we show that exogenous Spd induces a hyperpolarization‐activated Ca2+ current: the addition of Spd cannot induce the channel open probability increase in excised outside‐out patches, indicating that the effect of Spd in the induction of Ca2+ currents is exerted via a second messenger. This messenger is hydrogen peroxide (H2O2), and is generated during Spd oxidation, a reaction mediated by polyamine oxidase (PAO). These reactive oxygen species trigger the opening of the hyperpolarization‐activated Ca2+‐permeable channels in pollen. To provide further evidence that PAO is in fact responsible for the effect of Spd on the Ca2+‐permeable channels, two Arabidopsis mutants lacking expression of the peroxisomal‐encoding AtPAO3 gene, were isolated and characterized. Pollen from these mutants was unable to induce the opening of the Ca2+‐permeable channels in the presence of Spd, resulting in reduced pollen tube growth and seed number. However, a high Spd concentration triggers a Ca2+ influx beyond the optimal, which has a deleterious effect. These findings strongly suggest that the Spd‐derived H2O2 signals Ca2+ influx, thereby regulating pollen tube growth. 相似文献
9.
Hsiang‐Yu Yang Feng‐Zhi Lin Hui‐Wen Yang Pei‐Ling Yu Shih‐Ming Huang Yao‐Chang Chen Chien‐Sung Tsai Chih‐Yuan Lin 《Journal of cellular and molecular medicine》2020,24(12):6762-6772
This study addressed the hypothesis that cardiac Sirtuin 1 (Sirt1) deficiency alters cardiomyocyte Ca2+ and Na+ regulation, leading to cardiac dysfunction and arrhythmogenesis. We used mice with cardiac‐specific Sirt1 knockout (Sirt1?/?). Sirt1flox/flox mice were served as control. Sirt1?/? mice showed impaired cardiac ejection fraction with increased ventricular spontaneous activity and burst firing compared with those in control mice. The arrhythmic events were suppressed by KN93 and ranolazine. Reduction in Ca2+ transient amplitudes and sarcoplasmic reticulum (SR) Ca2+ stores, and increased SR Ca2+ leak were shown in the Sirt1?/? mice. Electrophysiological measurements were performed using patch‐clamp method. While L‐type Ca2+ current (ICa, L) was smaller in Sirt1?/? myocytes, reverse‐mode Na+/Ca2+ exchanger (NCX) current was larger compared with those in control myocytes. Late Na+ current (INa, L) was enhanced in the Sirt1?/? mice, alongside with elevated cytosolic Na+ level. Increased cytosolic and mitochondrial reactive oxygen species (ROS) were shown in Sirt1?/? mice. Sirt1?/? cardiomyocytes showed down‐regulation of L‐type Ca2+ channel α1c subunit (Cav1.2) and sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a), but up‐regulation of Ca2+/calmodulin‐dependent protein kinase II and NCX. In conclusions, these findings suggest that deficiency of Sirt1 impairs the regulation of intracellular Ca2+ and Na+ in cardiomyocytes, thereby provoking cardiac dysfunction and arrhythmogenesis. 相似文献
10.
Massimo Micaroni Giuseppe Perinetti Christopher P. Berrie Alexander A. Mironov 《Traffic (Copenhagen, Denmark)》2010,11(10):1315-1333
The Golgi apparatus (GA) is a dynamic store of Ca2+ that can be released into the cell cytosol. It can thus participate in the regulation of the Ca2+ concentration in the cytosol ([Ca2+]cyt), which might be critical for intra‐Golgi transport. Secretory pathway Ca2+‐ATPase pump type 1 (SPCA1) is important in Golgi homeostasis of Ca2+. The subcellular localization of SPCA1 appears to be GA specific, although its precise location within the GA is not known. Here, we show that SPCA1 is mostly excluded from the cores of the Golgi cisternae and is instead located mainly on the lateral rims of Golgi stacks, in tubular noncompact zones that interconnect different Golgi stacks, and within tubular parts of the trans Golgi network, suggesting a role in regulation of the local [Ca2+]cyt that is crucial for membrane fusion. SPCA1 knockdown by RNA interference induces GA fragmentation. These Golgi fragments lack the cis‐most and trans‐most cisternae and remain within the perinuclear region. This SPCA1 knockdown inhibits exit of vesicular stomatitis virus G‐protein from the GA and delays retrograde redistribution of the GA glycosylation enzymes into the endoplasmic reticulum caused by brefeldin A; however, exit of these enzymes from the endoplasmic reticulum is not affected. Thus, correct SPCA1 functioning is crucial to intra‐Golgi transport and maintenance of the Golgi ribbon. 相似文献
11.
Mizuno K Padma P Konno A Satouh Y Ogawa K Inaba K 《Biology of the cell / under the auspices of the European Cell Biology Organization》2009,101(2):91-103
Background information. Spermatozoa show several changes in flagellar waveform, such as upon fertilization. Ca2+ has been shown to play critical roles in modulating the waveforms of sperm flagella. However, a Ca2+‐binding protein in sperm flagella that regulates axonemal dyneins has not been fully characterized. Results. We identified a novel neuronal calcium sensor family protein, named calaxin (Ca2+‐binding axonemal protein), in sperm flagella of the ascidian Ciona intestinalis. Calaxin has three EF‐hand Ca2+‐binding motifs, and its orthologues are present in metazoan species, but not in yeast, green algae or plant. Immunolocalization revealed that calaxin is localized near the outer arm of the sperm flagellar axonemes. Moreover, it is distributed in adult tissues bearing epithelial cilia. An in vitro binding experiment indicated that calaxin binds to outer arm dynein. A cross‐linking experiment showed that calaxin binds to β‐tubulin in situ. Overlay experiments further indicated that calaxin binds the β‐dynein heavy chain of outer arm dynein in the presence of Ca2+. Conclusions. These results suggest that calaxin is a potential Ca2+‐dependent modulator of outer arm dynein in metazoan cilia and flagella. 相似文献
12.
Robert S. Siegel Shaowu Xue Yoshiyuki Murata Yingzhen Yang Noriyuki Nishimura Angela Wang Julian I. Schroeder 《The Plant journal : for cell and molecular biology》2009,59(2):207-220
Stomatal closure in response to abscisic acid depends on mechanisms that are mediated by intracellular [Ca2+] ([Ca2+]i), and also on mechanisms that are independent of [Ca2+]i in guard cells. In this study, we addressed three important questions with respect to these two predicted pathways in Arabidopsis thaliana. (i) How large is the relative abscisic acid (ABA)‐induced stomatal closure response in the [Ca2+]i‐elevation‐independent pathway? (ii) How do ABA‐insensitive mutants affect the [Ca2+]i‐elevation‐independent pathway? (iii) Does ABA enhance (prime) the Ca2+ sensitivity of anion and inward‐rectifying K+ channel regulation? We monitored stomatal responses to ABA while experimentally inhibiting [Ca2+]i elevations and clamping [Ca2+]i to resting levels. The absence of [Ca2+]i elevations was confirmed by ratiometric [Ca2+]i imaging experiments. ABA‐induced stomatal closure in the absence of [Ca2+]i elevations above the physiological resting [Ca2+]i showed only approximately 30% of the normal stomatal closure response, and was greatly slowed compared to the response in the presence of [Ca2+]i elevations. The ABA‐insensitive mutants ost1‐2, abi2‐1 and gca2 showed partial stomatal closure responses that correlate with [Ca2+]i‐dependent ABA signaling. Interestingly, patch‐clamp experiments showed that exposure of guard cells to ABA greatly enhances the ability of cytosolic Ca2+ to activate S‐type anion channels and down‐regulate inward‐rectifying K+ channels, providing strong evidence for a Ca2+ sensitivity priming hypothesis. The present study demonstrates and quantifies an attenuated and slowed ABA response when [Ca2+]i elevations are directly inhibited in guard cells. A minimal model is discussed, in which ABA enhances (primes) the [Ca2+]i sensitivity of stomatal closure mechanisms. 相似文献
13.
Cristina M. Velázquez‐Marrero Héctor G. Marrero José R. Lemos 《Journal of cellular physiology》2010,225(1):223-232
Release of neurotransmitter is activated by the influx of calcium. Inhibition of Ca2+ channels results in less calcium influx into the terminals and presumably a reduction in transmitter release. In the neurohypophysis (NH), Ca2+ channel kinetics, and the associated Ca2+ influx, is primarily controlled by membrane voltage and can be modulated, in a voltage‐dependent manner, by G‐protein subunits interacting with voltage‐gated calcium channels (VGCCs). In this series of experiments we test whether the κ‐ and µ‐opioid inhibition of Ca2+ currents in NH terminals is voltage‐dependent. Voltage‐dependent relief of G‐protein inhibition of VGCC can be achieved with either a depolarizing square pre‐pulse or by action potential waveforms. Both protocols were tested in the presence and absence of opioid agonists targeting the κ‐ and µ‐receptors in neurohypophysial terminals. The κ‐opioid VGCC inhibition is relieved by such pre‐pulses, suggesting that this receptor is involved in a voltage‐dependent membrane delimited pathway. In contrast, µ‐opioid inhibition of VGCC is not relieved by such pre‐pulses, indicating a voltage‐independent diffusible second‐messenger signaling pathway. Furthermore, relief of κ‐opioid inhibition during a physiologic action potential (AP) burst stimulation indicates the possibility of activity‐dependent modulation in vivo. Differences in the facilitation of Ca2+ channels due to specific G‐protein modulation during a burst of APs may contribute to the fine‐tuning of Ca2+‐dependent neuropeptide release in other CNS terminals, as well. J. Cell. Physiol. 225: 223–232, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
14.
Abstract. The albumen gland of the freshwater pulmonate snail Helisoma duryi produces and secretes the perivitelline fluid, which coats fertilized eggs and provides nutrients to the developing embryos. It is known that perivitelline fluid secretion is stimulated by dopamine through the activation of a dopamine D1‐like receptor, which in turn stimulates cAMP production leading to the secretion of perivitelline fluid. This paper examines the glandular release of perivitelline fluid and provides evidence for the role of Ca2+ in the regulated secretion of perivitelline fluid based on protein secretion experiments and inositol 1,4,5‐trisphosphate assays. Dopamine‐stimulated protein secretion by the albumen gland is reduced in Ca2+‐free medium or in the presence of plasma membrane Ca2+ channel blockers, although the Ca2+ channel subtype involved is unclear. In addition, dopamine‐stimulated protein secretion does not directly involve phospholipase C‐generated signaling pathways and Ca2+ release from intracellular stores. Sarcoplasmic/endoplasmic reticulum Ca2+‐ATPase inhibitors had little effect on protein secretion when applied alone; however, they potentiated dopamine‐stimulated protein secretion. Dantrolene, an inhibitor of ryanodine receptors, 8‐(N,N‐diethylamino)‐octyl‐3,4,5‐trimethoxybenzoate hydrochloride, a nonspecific inhibitor of intracellular Ca2+ channels, and 2‐aminoethyldiphenylborate, an inhibitor of inositol 1,4,5‐trisphosphate receptors, did not suppress protein secretion, suggesting Ca2+ release from internal stores does not directly regulate protein secretion. Thus, the influx of Ca2+ from the extracellular space appears to be the major pathway mediating protein secretion by the albumen gland. The results are discussed with respect to the role of Ca2+ in controlling exocytosis of proteins from the albumen gland secretory cells. 相似文献
15.
Yu Y Halet G Lai FA Swann K 《Biology of the cell / under the auspices of the European Cell Biology Organization》2008,100(11):633-643
Background information. At fertilization in mammalian eggs, the sperm induces a series of Ca2+ oscillations via the production of inositol 1,4,5‐trisphosphate. Increased inositol 1,4,5‐trisphosphate production appears to be triggered by a sperm‐derived PLCζ (phospholipase C‐ζ) that enters the egg after gamete fusion. The specific phosphatidylinositol 4,5‐bisphosphate hydrolytic activity of PLCζ implies that DAG (diacylglycerol) production, and hence PKC (protein kinase C) stimulation, also occurs during mammalian egg fertilization. Fertilization‐mediated increase in PKC activity has been demonstrated; however, its precise role is unclear. Results. We investigated PLCζ‐ and fertilization‐mediated generation of DAG in mouse eggs by monitoring plasma‐membrane translocation of a fluorescent DAG‐specific reporter. Consistent plasma‐membrane DAG formation at fertilization, or after injection of physiological concentrations of PLCζ, was barely detectable. However, when PLCζ is overexpressed in eggs, significant plasma‐membrane DAG production occurs in concert with a series of unexpected secondary high‐frequency Ca2+ oscillations. We show that these secondary Ca2+ oscillations can be mimicked in a variety of situations by the stimulation of PKC and that they can be prevented by PKC inhibition. The way PKC leads to secondary Ca2+ oscillations appears to involve Ca2+ influx and the loading of thapsigargin‐sensitive Ca2+ stores. Conclusions. Our results suggest that overproduction of DAG in PLCζ‐injected eggs can lead to PKC‐mediated Ca2+ influx and subsequent overloading of Ca2+ stores. These results suggest that DAG generation in the plasma membrane of fertilizing mouse eggs is minimized since it can perturb egg Ca2+ homoeostasis via excessive Ca2+ influx. 相似文献
16.
J. T. P. ALBRECHTOVÁ S. HEILSCHER L. LESKE P. WALCZYSKO & E. WAGNER 《Plant, cell & environment》2003,26(12):1985-1994
The apical meristem of the short‐day plant Chenopodium rubrum responds to photoperiodic flower induction with specific changes of pH and Ca2+ patterning immediately after the inductive dark span. The red–far‐red reversibility of the pH and Ca2+ patterning in response to night break treatments was measured in order to distinguish between the effect of the prolonged dark span per se and the specific effect of photoperiodic flower induction. In addition, the pH and Ca2+ patterning in C. rubrum was compared with the long‐day plant Chenopodium murale. The pH was visualized using the fluorescent probe carboxy SNARF‐1. Calcium ion concentrations were studied using a combination of Ca2+‐probes Fluo‐3 and Fura Red. It was observed that the specific changes in pH and Ca2+ patterning at the apical meristem of C. rubrum were abolished by the red‐light break. This effect was fully reversed with a subsequent single far‐red treatment. These observations infer the influence of phytochrome on both pH and Ca2+ patterning. Changes in pH and Ca2+ patterning upon flower induction were observed in both long‐day and short‐day plants. These results support the hypothesis that changes of pH and [Ca2+] in cells of the apical meristem are part of the pathway in signal transduction triggering flower initiation. 相似文献
17.
Stanley A. Mendoza Abelardo Lopez-Rivas James W. Sinnett-Smith Enrique Rozengurt 《Experimental cell research》1986,164(2)
Vasopressin increased intracellular free calcium concentration [Ca2+]i in quin-2-loaded quiescent Swiss 3T3 cells. This effect of vasopressin was rapidly inhibited by biologically active tumour promoters including phorbol dibutyrate (PBt2) and by the synthetic diacylglycerol 1-oleoyl-2-acetyl-glycerol (OAG). Prolonged pretreatment of Swiss 3T3 cells with PBt2 causes a loss of protein kinase C activity (Rodriguez-Pena & Rozengurt, Biochem biophys res commun 120 (1984) 1053) [28]. This pretreatment abolished the inhibition by PBt2 or OAG of vasopressin-mediated increases in Ca2+]i. Vasopressin also stimulated 45Ca2+ efflux from cells pre-loaded with the isotope. This effect of the hormone was also inhibited by PBt2. Prolonged pretreatment with PBt2 prevented the inhibition of vasopressin-stimulated 45Ca2+ release by PBt2. Thus, protein kinase C stimulation inhibits vasopressin-mediated increases in [Ca2+]i and 45Ca2+ efflux apparently by blocking the increased release of Ca2+ from an intracellular store caused by the hormone. These findings suggest that activation of protein kinase C may act as a feedback inhibitor to modulate ligand-mediated increases in [Ca2+]i. 相似文献
18.
The Shigella type III effector IpgD recodes Ca2+ signals during invasion of epithelial cells
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Chun Hui Sun Benjamin Wacquier Daniel I Aguilar Nathalie Carayol Kevin Denis Sylviane Boucherie Cesar Valencia‐Gallardo Ceren Simsek Christophe Erneux Alexandre Lehman Jost Enninga Laurence Arbibe Philippe Sansonetti Geneviève Dupont Guy Tran Van Nhieu 《The EMBO journal》2017,36(17):2567-2580
The role of second messengers in the diversion of cellular processes by pathogens remains poorly studied despite their importance. Among these, Ca2+ virtually regulates all known cell processes, including cytoskeletal reorganization, inflammation, or cell death pathways. Under physiological conditions, cytosolic Ca2+ increases are transient and oscillatory, defining the so‐called Ca2+ code that links cell responses to specific Ca2+ oscillatory patterns. During cell invasion, Shigella induces atypical local and global Ca2+ signals. Here, we show that by hydrolyzing phosphatidylinositol‐(4,5)bisphosphate, the Shigella type III effector IpgD dampens inositol‐(1,4,5)trisphosphate (InsP3) levels. By modifying InsP3 dynamics and diffusion, IpgD favors the elicitation of long‐lasting local Ca2+ signals at Shigella invasion sites and converts Shigella‐induced global oscillatory responses into erratic responses with atypical dynamics and amplitude. Furthermore, IpgD eventually inhibits InsP3‐dependent responses during prolonged infection kinetics. IpgD thus acts as a pathogen regulator of the Ca2+ code implicated in a versatility of cell functions. Consistent with this function, IpgD prevents the Ca2+‐dependent activation of calpain, thereby preserving the integrity of cell adhesion structures during the early stages of infection. 相似文献
19.
Ca2+‐independent sortase‐A exhibits high selective protein ligation activity in the cytoplasm of Escherichia coli
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A Staphylococcus aureus transpeptidase, sortase A (SrtA), which catalyzes a peptide ligation with high substrate specificity, is a useful tool to site‐specifically attach proteinaceous/peptidic functional molecules to target proteins. However, its strong Ca2+ dependency makes SrtA difficult for use under low Ca2+ concentrations and in the presence of Ca2+‐binding substances. To overcome this problem, we designed a SrtA mutant that Ca2+‐independently demonstrates a high catalytic activity. The heptamutant (P94R/E105K/E108A/D160N/D165A/K190E/K196T), which resulted from a combination of known mutations at the Ca2+‐binding site and around the substrate‐binding site, successfully catalyzed a selective protein‐protein ligation in the cytoplasm of Escherichia coli. Selective protein modification in living cells is a promising approach for investigating cellular events and regulating cell functions. This SrtA mutant may prove to be a versatile tool for adding new functionalities to proteins of interest by incorporating functional proteins and chemically modified peptides in living cells, which usually retain low Ca2+ concentrations. 相似文献
20.
Peng Tu†‡ Christiane Kunert-Keil§ Silke Lucke§ Heinrich Brinkmeier§ Alexandre Bouron†‡ 《Journal of neurochemistry》2009,108(1):126-138
The lipid diacylglycerol (DAG) analogue 1‐oleoyl‐2‐acetyl‐sn‐glycerol (OAG) was used to verify the existence of DAG‐sensitive channels in cortical neurons dissociated from E13 mouse embryos. Calcium imaging experiments showed that OAG increased the cytosolic concentration of Ca2+ ([Ca2+]i) in nearly 35% of the KCl‐responsive cells. These Ca2+ responses disappeared in a Ca2+‐free medium supplemented with EGTA. Mn2+ quench experiments showed that OAG activated Ca2+‐conducting channels that were also permeant to Ba2+. The OAG‐induced Ca2+ responses were unaffected by nifedipine or omega‐conotoxin GVIA (Sigma‐Aldrich, Saint‐Quentin Fallavier, France) but blocked by 1‐[β‐(3‐(4‐Methoxyphenyl)propoxy)‐4‐methoxyphenethyl]‐1H‐imidazole hydrochloride (SKF)‐96365 and Gd3+. Replacing Na+ ions with N‐methyl‐d ‐glucamine diminished the amplitude of the OAG‐induced Ca2+ responses showing that the Ca2+ entry was mediated via Na+‐dependent and Na+‐independent mechanisms. Experiments carried out with the fluorescent Na+ indicator CoroNa Green showed that OAG elevated [Na+]i. Like OAG, the DAG lipase inhibitor RHC80267 increased [Ca2+]i but not the protein kinase C activator phorbol 12‐myristate 13‐acetate. Moreover, the OAG‐induced Ca2+ responses were not regulated by protein kinase C activation or inhibition but they were augmented by flufenamic acid which increases currents through C‐type transient receptor potential protein family (TRPC) 6 channels. In addition, application of hyperforin, a specific activator of TRPC6 channels, elevated [Ca2+]i. Whole‐cell patch‐clamp recordings showed that hyperforin activated non‐selective cation channels. They were blocked by SKF‐96365 but potentiated by flufenamic acid. Altogether, our data show the presence of hyperforin‐ and OAG‐sensitive Ca2+‐permeable channels displaying TRPC6‐like properties. This is the first report revealing the existence of second messenger‐operated channels in cortical neurons. 相似文献